Exhaust system for internal combustion engine

FIELD OF THE INVENTION

0001The present invention is related to an exhaust system for an internal combustion engine. In particular, the present invention is related to an exhaust system that monitors performance of a particulate filter and/or an oxidation catalyst.

BACKGROUND OF THE INVENTION

0002Legislation and statutory regulations require self-monitoring capabilities, for example onboard diagnosis, to monitor motor vehicle emissions of hydrocarbons, carbon monoxide, nitrogen oxides, particulates, and the like. In order to comply with such legal requirements, diagnosis functions are typically integrated within an engine management system for a motor vehicle internal combustion engine. Such management systems typically determine the ongoing performance of exhaust system components such as catalytic converters, nitrogen oxide catalysts, particulate filters and the like.

0003Currently available diagnostic systems for current and future exhaust aftertreatment systems have significant challenges in attempting to meet future/anticipated statutory emission standards. For example, future diagnostic requirements for diesel engines will require failure detection of a diesel particulate filter (DPF) with a particulate matter deterioration factor as low as 2.5. However, conventional measurement methodologies, for example differential pressure sensors, can only detect particulate matter deterioration factors between 10 to 20. As such, current particulate matter sensor technology does not provide an adequate solution for desired DPF failure detection.

0004The control and/or detection of non-methane hydrocarbons (NMHC) poses similar challenges to current technology. The detection of NMHC is currently afforded through indirect measurement since NMHC sensors are not available. As such, excessive NMHC emissions are typically tracked through intrusive tests which focus on the exothermic reaction generated during oxidation of the NMHC on a catalytic coating of a catalytic converter and/or DPF. Therefore, an exhaust system that provides for desired DPF failure detection and NMHC monitoring, and yet is simple in design, robust, etc., would be desirable.

SUMMARY OF THE INVENTION

0005The present invention discloses an exhaust system for an internal combustion engine that provides failure detection of a particulate filter and/or monitoring of non-methane hydrocarbons (NMHC) for an internal combustion engine. The exhaust system can include a main exhaust duct and a secondary exhaust line, both of which are operative for exhaust gas to pass therethrough. The system has an oxidation catalyst and a main particulate filter located within and/or inline with the main exhaust duct. A monitoring particulate filter is also included and located within and/or inline with the secondary exhaust line. All of the exhaust gas passing through the main exhaust duct passes through the main particulate filter and the secondary exhaust line and the monitoring particulate filter are located downstream from the main particulate filter.

0006A generally small portion of the exhaust gas passing through the main exhaust duct, and thus through the main particulate filter, can be used and/or directed to pass through the monitoring particulate filter. A pressure sensor operative to detect a change in pressure between an upstream side and a downstream side of the monitoring particulate filter, as well as a temperature sensor operative to detect a change in temperature between the upstream side and the downstream side of the monitoring particulate filter, can be included.

0007An increase in pressure across the monitoring particulate filter detected by the pressure sensor can indicate a decrease in performance and/or failure of the main particulate filter, while an increase in temperature detected by the temperature sensor can indicate a decrease in performance of the oxidation catalyst and/or an excess of NMHC passing through the oxidation catalyst.

0008With a generally small portion of exhaust gas passing through the monitoring particulate filter, a generally small particulate filter can be used to monitor the main particulate filter. It is appreciated that a generally small monitoring particulate filter can reduce the cost associated with an exhaust system that monitors performance of a particulate filter and/or an oxidation catalyst. In addition, a generally small monitoring particulate filter can have a heavy catalyst loading without a large increase in cost. In this manner, a monitoring particulate filter with a large catalyst loading can be used to oxidize NMHC passing therethrough, the oxidation of the NMHC affording for an increase in temperature which can be detected by the temperature sensor.

0009In the event that the main particulate filter fails and/or starts to fail, and particulates pass therethrough, at least part of the particulates that have passed through the mainparticulate filter can enter the monitoring particulate filter. The increase of particulate loading in the monitoring particulate filter can result in an increase in pressure between the upstream side and the downstream side of the filter. In addition, the increase in pressure can be monitored and/or detected and used to alert an operator, driver, service person, etc, of the failure and/or potential failure of the main particulate filter. In a like manner, an increase in NMHC passing through the monitoring particulate filter can result in an increase in the oxidation thereof and thus an increase in temperature of the filter. The increase in temperature can also be used to determine the ongoing performance of the oxidation catalyst, the internal combustion engine and the like.

0010In some instances, a pump in fluid communication with the secondary exhaust line can be included and be operative to force exhaust gas through the monitoring particulate filter at a generally constant flow rate. It is appreciated that a generally constant flow rate can afford a decrease in catalyst loading of the monitoring particulate filter since the oxidation of NMHC passing therethrough can be controlled with greater accuracy than for NMHC passing through the filter at a generally non-constant flow rate. In the alternative to a pump, a venturi can also be in fluid communication with the secondary exhaust line and be operative to pull exhaust gas through the monitoring particulate filter at a generally constant flow rate.

0011It is appreciated that one or more mixing devices can be located downstream from the main particulate filter and upstream from the secondary exhaust line in order to ensure a representative sampling of exhaust gas passing through the main particulate filter flows into the monitoring particulate filter. In some instances, less than 25% of the exhaust gas that passes through the main particulate filter enters and flows through the secondary exhaust line and the monitoring particulate filter. In other instances, less than 10%, and in still other instances less than 5%, of the exhaust gas that passes through the main particulate filter enters and flows through the monitoring particulate filter.

0012A process for monitoring an exhaust system of an internal combustion engine is also disclosed. The process includes providing exhaust ducting operative for exhaust gas to flow therethrough from the internal combustion engine to a pressure sink. The exhaust ducting can have a main exhaust duct and a secondary exhaust line and a main particulate filter can be located within and/or inline the main exhaust duct between the engine and the pressure sink. A monitoring particulate filter can be provided and located within and/or inline with the secondary exhaust line and the secondary exhaust line with the monitoring particulate filter can be located downstream of the main particulate filter. A pressure sensor operative to detect a change in pressure between an upstream side and a downstream side of the monitoring particulate filter can be included and used to detect a change in pressure across the monitoring particulate filter. As stated above, an increase in pressure across the monitoring particulate filter can be the result of a failing and/or failed main particulate filter. A temperature sensor can also be provided and be operative to detect a change in temperature across the monitoring particulate filter.

0013Upon operation of the internal combustion engine, exhaust gas can flow through the exhaust ducting from the engine, through the main particulate filter to the pressure sink. A portion of the exhaust gas passing through the main particulate filter can flow through the secondary exhaust line and thus into the monitoring particulate filter. As such, pressure and temperature changes across the monitoring particulate filter can be detected and/or monitored and thereby provide information on the performance of the main particulate filter and oxidation catalyst, respectively, located upstream from the monitoring particulate filter.

BRIEF DESCRIPTION OF THE DRAWINGS

0014<figref idref="DRAWINGS">FIG. 1</figref> is a schematic diagram representing an internal combustion engine having an exhaust system according to an embodiment of the present invention;

0015<figref idref="DRAWINGS">FIG. 2</figref> is a schematic diagram representing another embodiment of the present invention;

0016<figref idref="DRAWINGS">FIG. 3</figref> is a schematic diagram representing another embodiment of the present invention;

0017<figref idref="DRAWINGS">FIG. 4</figref> is a schematic diagram representing another embodiment of the present invention;

0018<figref idref="DRAWINGS">FIG. 5</figref> is a schematic diagram representing another embodiment of the present invention;

0019<figref idref="DRAWINGS">FIG. 6</figref> is a schematic diagram representing another embodiment of the present invention;

0020<figref idref="DRAWINGS">FIG. 7</figref> is a schematic diagram representing another embodiment of the present invention;

0021<figref idref="DRAWINGS">FIG. 8</figref> is a schematic diagram representing three possible embodiments for taking a portion of an exhaust gas from a main exhaust duct and passing it into a secondary exhaust line;

0022<figref idref="DRAWINGS">FIG. 9</figref> is an end cross-sectional view of the section labeled <b>9</b>-<b>9</b> in <figref idref="DRAWINGS">FIG. 8</figref>;

0023<figref idref="DRAWINGS">FIG. 10</figref> is an end cross-sectional view of the section labeled <b>10</b>-<b>10</b> in <figref idref="DRAWINGS">FIG. 8</figref>; and

0024<figref idref="DRAWINGS">FIG. 11</figref> is an end cross-sectional view of the area labeled <b>11</b>-<b>11</b> in <figref idref="DRAWINGS">FIG. 8</figref>.

DETAILED DESCRIPTION OF THE INVENTION

0025The present invention discloses an exhaust system and a process operative to monitor a particulate filter located within and/or inline a main exhaust duct. As such, the exhaust system and process have utility for providing exhaust gas aftertreatment.

0026The exhaust system includes a main exhaust duct and a secondary exhaust line, both of which are operative for exhaust gas to pass therethrough. An oxidation catalyst and/or a main particulate filter can be located within and/or inline with the main exhaust duct. A monitoring particulate filter can be located within and/or inline the secondary exhaust line. In addition, the secondary exhaust line and the monitoring particulate filter can be located downstream from the main particulate filter and at least a portion of the exhaust gas that passes through the main particulate filter can pass through the secondary exhaust line and the monitoring particulate filter. It is appreciated that the term “inline” refers to a component, for example the main particulate filer, oxidation catalyst, monitoring particulate filer, etc., being in fluid communication with the main exhaust duct or secondary exhaust line without a bypass being present around the component.

0027A pressure sensor that is operative to detect a change in pressure between an upstream side and a downstream side of the monitoring particulate filter affords for monitoring of the pressure across the filter. In addition, a temperature sensor is provided that can detect a change in temperature between the upstream side and the downstream side of the monitoring particulate filter.

0028In the event that the main particulate filter starts to fail and/or fails such that excess particulates pass therethrough, at least a portion of the particulates can enter the monitoring particulate filter located downstream from the main particulate filter and afford a pressure increase across the monitoring particulate filer. In addition, initiation and/or total failure of the oxidation catalysts can afford an increase of nonmethane hydrocarbons (NMHC) passing therethrough, and thus a corresponding increase in temperature across the monitoring particulate filter can occur when excess NMHC is oxidized therewithin. It is appreciated that the monitoring particulate filter can have a catalyst loading therewithin for the oxidation of the NMHC, the oxidation affording an increase in temperature. In addition, the catalayst loading of the monitoring particulate filter can be greater than catalyst loading of the oxidation catalyst, thereby ensuring the oxidation of excess NMHC passing through the monitoring particulate filter. For example, the catalyst loading of the monitoring particulate filter can be greater than 20% of the catalyst loading of the oxidation catalyst, and yet with the reduced size of the monitoring particulate filter, a significant increase in cost is avoided.

0029The exhaust system can also include a pump that is in fluid communication with the secondary exhaust line and is operative to force exhaust gas through the monitoring particulate filter at a generally constant flow rate. In the alternative, a venturi can be in fluid communication with the secondary exhaust line in order to pull exhaust gas through the monitoring particulate filter at a generally constant flow rate. In some instances, one or more mixing devices can be located downstream from the main particulate filter and upstream from the secondary exhaust line in order to ensure that a representative sample of the exhaust gas passing through the main particulate filter enters into the secondary exhaust line and thus into the monitoring particulate filter.

0030A generally small portion of the exhaust gas that passes through the main particulate filter can be used to pass through the monitoring particulate filter. In some instances, less than 25% of the exhaust gas that passes through the main particulate filter can be used to enter and flow through the secondary exhaust line and thus pass through the monitoring particulate filter. In other instances, less than 10%, and in still yet other instances less than 5%, of the exhaust gas that passes through the main particulate filter can be used to enter and flow through the secondary exhaust line and thus the monitoring particulate filter. In this manner, a relatively small particulate filter can be used to monitor the performance of the main particulate filter and/or the oxidation catalyst.

0031A process for monitoring the exhaust system and exhaust gas of the internal combustion engine can include providing exhaust ducting that is operative for exhaust gas to flow therethrough from the internal combustion engine to a pressure sink. The exhaust ducting can have a main exhaust duct and a secondary exhaust line that is in fluid communication with the main exhaust duct. An oxidation catalyst, main particulate filter, and the like can be provided as described above and located within and/or inline with the main exhaust duct. In addition, a monitoring particulate filter can be located within and/or inline with the secondary exhaust line. A pressure sensor and a temperature sensor that are operative to detect a change in pressure and temperature, respectively, across the monitoring particulate filter are also provided as part of the process.

0032Upon operation of the internal combustion engine, exhaust gas can flow through the exhaust ducting from the engine, through the main particulate filter, to the pressure sink. A portion of the exhaust gas flowing through the main particulate filter can pass or flow into the secondary exhaust line and thus into the monitoring particulate filter. Monitoring of the pressure sensor and/or temperature sensor can provide information as to when there is an increase in pressure and/or an increase in temperature across the main particulate filter and oxidation catalyst, respectively. It is appreciated that an increase in pressure and/or temperature can be used as an alert for the initiation and/or complete failure of the main particulate filter and/or oxidation catalyst, respectively.

0033The system and the process afford for all of the exhaust gas in the main exhaust duct to pass through the main particulate filter. Stated differently, there is no bypass around the main particulate filter for any of the exhaust gas to pass through. In addition, the system and the process are simple in design, robust, and can use well-known components that have been certified for vehicle lifetime operation, and thus do not require additional and/or new certification. It is appreciated that such a system and process can be easy to retrofit to existing internal combustion engines. In some instances, the internal combustion engine is a diesel engine and the oxidation catalyst is a diesel oxidation catalyst (DOC), the particulate filter is a diesel particulate filter (DPF), and the like.

0034Turning now to <figref idref="DRAWINGS">FIG. 1</figref>, an embodiment of an exhaust system is shown generally at reference numeral <b>10</b>. The exhaust system <b>10</b> can include exhaust ducting <b>200</b> in fluid communication with an internal combustion engine <b>100</b>. In some instances, the internal combustion engine <b>100</b> can be a diesel engine with a turbocharger <b>110</b> and an intercooler <b>120</b>. The turbocharger <b>110</b> can have a low pressure inlet <b>112</b> and a high pressure outlet <b>114</b>.

0035The exhaust ducting <b>200</b> can have a main exhaust duct <b>210</b>, a diesel oxidation catalyst (DOC) <b>220</b>, a diesel particulate filter (DPF) <b>230</b> and a nitrogen oxide catalyst (DeNOx) <b>240</b>. It is appreciated that exhaust gas exits the engine <b>100</b> through the main exhaust duct <b>210</b> and flows or travels to a pressure sink <b>1</b>. At a location between the DPF <b>230</b> and the pressure sink <b>1</b>, a secondary exhaust line <b>250</b> can be located, the secondary exhaust line <b>250</b> in fluid communication with the main exhaust duct <b>210</b>. Within and/or inline with the secondary exhaust line <b>250</b> is a monitoring diesel particulate filter (MDPF) <b>260</b>.

0036In some instances, a pressure sensor <b>262</b> can be included that affords for the detection and monitoring of a pressure difference across the MDPF <b>260</b>. For example, a pressure sensor <b>262</b> can be located on a downstream side <b>261</b> and another pressure sensor <b>262</b> can be located on an upstream side <b>263</b>. In the alternative, if a pressure on the downstream side <b>261</b> is generally known and/or is generally constant, a single pressure sensor <b>262</b> can be located on the upstream side <b>263</b> and used to monitor a pressure change across the MDPF <b>260</b>. In another alternative, if a pressure on the upstream side <b>263</b> is generally known and/or is generally constant, a single pressure sensor <b>262</b> can be located on the downstream side <b>261</b> and used to monitor a change in pressure across the MDPF <b>260</b>. It is appreciated that such alternatives are different examples, embodiments, etc., that afford for a pressure change to be detected and/or monitored across the MDPF <b>260</b>, e.g. when an increase of particulate matter passes or flows into the MDPF <b>260</b>. It is further appreciated that a pressure monitor that can calculate and/or determine an increase in pressure between the downstream side <b>261</b> and the upstream side <b>263</b> using the one or more pressure sensors <b>262</b> can be included.

0037In some instances, a temperature sensor <b>264</b> can be included that affords for the detection and monitoring of a temperature difference across the MDPF <b>260</b>. For example, a temperature sensor <b>264</b> can be located on the downstream side <b>261</b> and another temperature sensor <b>264</b> can be located on the upstream side <b>263</b>. In the alternative, if a temperature on the downstream side <b>261</b> is generally known and/or is generally constant, a single temperature sensor <b>264</b> can be located on the upstream side <b>263</b> and used to monitor a temperature change across the MDPF <b>260</b>. In another alternative, if a temperature on the upstream side <b>263</b> is generally known and/or is generally constant, a temperature sensor <b>264</b> can be located on the downstream side <b>261</b> and used to monitor a change in temperature across the MDPF <b>260</b>. It is appreciated that such alternatives are different examples, embodiments, etc, that afford for a temperature change to be detected and/or monitored across the MDPF <b>260</b> when an increase of hydrocarbons passes thereinto. It is further appreciated that a temperature monitor that can calculate and/or determine an increase in temperature between the downstream side <b>261</b> and the upstream side <b>263</b> using the one or more temperature sensors <b>264</b> can be included.

0038During operation of the internal combustion engine <b>100</b>, exhaust gas exits therefrom and flows through the main exhaust duct <b>210</b>, through the DOC <b>220</b>, DPF <b>230</b>, and DeNOx <b>240</b>. At least part of the exhaust gas can be diverted to flow into the secondary exhaust line <b>250</b> and thus through the MDPF <b>260</b>. In the event that the DOC <b>220</b> is not operating properly and/or excessive hydrocarbons, for example NMHC, pass through the DOC <b>220</b>, at least a portion thereof can pass or flow into the secondary exhaust line <b>250</b> and the MDPF <b>260</b>. The MDPF <b>260</b> can have catalyst loading therewithin that affords for the oxidation of the NMHC, thereby producing a corresponding increase in the temperature of the MDPF <b>260</b>. It is appreciated that the increase in temperature of the MDPF <b>260</b> can be detected and/or monitored and used as an alert related to the operation of the DOC <b>220</b>. In this manner, the performance of the DOC <b>220</b> can be monitored.

0039In the event that the DPF <b>230</b> begins to diminish in its performance, e.g. starts to fail or does fail, diesel particulates will exit the DPF <b>230</b> and a portion thereof can pass or flow into the secondary exhaust line <b>250</b> and thus the MDPF <b>260</b>. Upon entering the MDPF <b>260</b>, a pressure increase across the filter can occur and be detected by the pressure sensor <b>262</b>. In this manner, performance of the DPF <b>230</b> can be detected and monitored. It is appreciated that the secondary exhaust line <b>250</b> can extend from the MDPF <b>260</b> to the low pressure inlet <b>112</b> of the turbocharger <b>110</b> as shown in <figref idref="DRAWINGS">FIG. 1</figref>.

0040Turning now to <figref idref="DRAWINGS">FIG. 2</figref> where like numerals represent like components as described above, an embodiment <b>20</b> is shown with a throttle <b>270</b> in line with the main exhaust duct <b>210</b>.

0041<figref idref="DRAWINGS">FIG. 3</figref> illustrates an embodiment <b>30</b> with a pump <b>280</b> located downstream from the MDPF <b>260</b> and in fluid communication with the secondary exhaust line <b>250</b>. It is appreciated that the pump <b>280</b> can force exhaust gas through the MDPF <b>260</b> at a generally constant flow rate. Although the pump <b>280</b> is shown downstream from the MDPF <b>260</b> in this figure, it is appreciated that a pump can be located upstream of the MDPF <b>260</b>. It is further appreciated that with a constant flow rate of exhaust gas through the MDPF <b>260</b>, oxidation of excess hydrocarbons passing into the MDPF <b>260</b> can be provided with less catalyst loading of the filter <b>260</b>.

0042Instead of using a pump <b>280</b>, a venturi <b>290</b> can be in fluid communication with the MDPF <b>260</b> as shown in embodiment <b>40</b> illustrated in <figref idref="DRAWINGS">FIG. 4</figref>. In this manner, the venturi <b>290</b> can pull exhaust gas through the MDPF <b>260</b> at a generally constant flow rate and allow for less catalyst loading of the filter <b>260</b> as taught above.

0043Turning now to <figref idref="DRAWINGS">FIG. 5</figref>, an embodiment <b>50</b> illustrates that exhaust gas passing through the MDPF <b>260</b> is not required to pass through the turbocharger <b>110</b> and/or a component located downstream from the DPF <b>230</b> and inline with the main exhaust duct <b>210</b>. For example, the exhaust gas passing through the MDPF <b>260</b> could be exited to the atmosphere, returned to the main exhaust line <b>210</b> and the like.

0044Referring now to <figref idref="DRAWINGS">FIG. 6</figref>, an embodiment <b>60</b> illustrates that the MDPF <b>260</b> can be located inside the main exhaust duct <b>210</b>. The embodiment <b>60</b> affords for a portion of the exhaust gas that has passed through the DPF <b>230</b> to bypass the MDPF <b>260</b> and a portion of the exhaust gas to flow into the MDPF <b>260</b>. It is appreciated that although the MDPF <b>260</b> is located within the main exhaust duct <b>210</b>, the pressure sensor <b>262</b>, and the temperature sensor <b>264</b> can still provide a change in pressure and temperature, respectively, across the filter and thus afford for monitoring of the performance of the DOC <b>220</b> and the DPF <b>230</b> as taught above.

0045An embodiment <b>70</b> of an exhaust system is shown in <figref idref="DRAWINGS">FIG. 7</figref> where the MDPF <b>260</b> is located downstream from the DeNOx <b>240</b>. It is appreciated that although the MDPF <b>260</b> shown in this figure is in line with the main exhaust duct <b>210</b>, this is not required. For example, the embodiments shown in <figref idref="DRAWINGS">FIGS. 1-6</figref> could have the MDPF <b>260</b> located downstream from the DeNOx <b>240</b>. In addition, it is appreciated that the exact order of the DOC <b>220</b>, DPF <b>230</b>, and DeNOx <b>240</b> with respect to their position along the main exhaust line <b>210</b> can be different than illustrated in the figures. For example, the DeNOx <b>240</b> could be located upstream of the MDPF <b>260</b>.

0046Referring now to <figref idref="DRAWINGS">FIGS. 8-11</figref>, three separate examples of the secondary exhaust line <b>250</b> in fluid communication with the main exhaust line <b>210</b> are shown. As shown in <figref idref="DRAWINGS">FIG. 9</figref>, the secondary exhaust line <b>250</b> can have an inlet portion <b>254</b> that is located at least partially within the main exhaust duct <b>210</b>. The inlet portion <b>254</b> can have a bend such that an inlet end <b>255</b> faces upstream and thus affords for a portion of the exhaust gas that has passed through the DPF <b>230</b> to enter into the secondary exhaust line <b>250</b>. With respect to <figref idref="DRAWINGS">FIG. 10</figref>, the secondary exhaust line <b>250</b> can have an inlet portion <b>254</b> that has a slot <b>258</b> in the wall thereof. In this manner, the slot <b>258</b> can be arranged such that it faces upstream. With respect to <figref idref="DRAWINGS">FIG. 11</figref>, the secondary exhaust line <b>250</b> can have an inlet portion <b>254</b> with one or more apertures <b>259</b> that can face upstream and allow exhaust gas to flow into the secondary exhaust line <b>250</b>.

0047It is appreciated that a valve (not shown) can be included at least partially within the secondary exhaust line <b>250</b> upstream of the MDPF <b>260</b>. The valve can terminate or stop any flow of the exhaust gas that has passed through the DPF <b>230</b> from passing through the MDPF <b>260</b>. In this manner, when the DPF <b>230</b> is exposed to a high stress, for example during regeneration, the MDPF <b>260</b> can be deactivated in order to avoid failure thereof. In addition, once a DPF <b>230</b> is known to fail, the MDPF <b>260</b> could be deactivated such that it will not fail also.

0048It is appreciated that since the MDPF <b>260</b> does not have all of the exhaust gas flowing through the main exhaust duct <b>210</b> passing therethrough, it can be significantly smaller in size than the MPF <b>230</b>. In addition, due to its smaller size, a high loading of active metal, for example platinum, palladium, and the like, can be provided and yet remain cost effective. For example and for illustrative purposes only, the MDPF <b>260</b> can have a catalyst loading in the range of 75 to 150 g/ft³, for example 100 g/ft³, whereas a typical catalyst loading for the DPF <b>230</b> can be generally 50 g/ft³. If the MDPF <b>260</b> is driven without a throttle valve, it is appreciated that the MDPF <b>260</b> will not increase any back pressure to the system. As such, the design of the MDPF <b>260</b> can be adjusted to exhibit good filtering and pressure change detection since a generally low pressure change can be detected across the filter.

0049It is further appreciated that one or mixing devices (not shown) can be located upstream from the secondary exhaust line <b>250</b> such that exhaust gas passing through the DPF <b>230</b> is properly mixed before passing or flowing into the MDPF <b>260</b>. Such a mixing device can include a fixed vane, a swirled vane, and the like, the mixing device located and optionally rigidly attached to an interior wall of the main exhaust duct <b>210</b>.

0050During operation, a portion of the exhaust gas passing through the DPF <b>230</b> is diverted from the main exhaust duct <b>210</b> and into the secondary exhaust line <b>250</b>. The exhaust gas flowing into the secondary exhaust line <b>250</b> can then pass or enter into the MDPF <b>260</b>. In the event that excess particulate matter passes into the MDPF <b>260</b>, a pressure increase can occur between the upstream side and the downstream side thereof. The pressure increase can be detected by the pressure sensor <b>262</b> and used to alert an onboard diagnostic system that excess particulate matter is exiting the DPF <b>230</b> and thus provide a warning that the DPF <b>230</b> is failing or has already failed. In a like manner, the catalyst loading of the MDPF <b>260</b> can oxidize hydrocarbons passing therethrough and result in an increase in temperature from the upstream side to the downstream side. The change in temperature can be detected by one or more temperature sensors <b>264</b>. In this manner, an increase in temperature across the MDPF <b>260</b> can provide information to the onboard diagnostic system that the DOC <b>220</b> is failing and/or has already failed.

0051The components of the MDPF <b>260</b>, pressure sensor <b>262</b>, temperature sensor <b>264</b>, and secondary exhaust line <b>250</b> can be components that are currently available on the market. In addition, such components can have existing vehicle life certification such that recertification of the system and/or process is not required. Therefore, the system and/or process is appreciated to be useful for retrofitting of existing systems and for use with new systems.

0052It is to be understood that various modifications are readily made to the embodiments of the present invention described herein without departing from the scope and spirit thereof. Methods, apparatus, compositions, systems, and the like described herein are exemplary and not intended as limitations on the scope of the invention. Changes therein and other uses will occur to those skilled in the art. The scope of the invention is defined by the scope of the claims.